Engines are required to operate under increasingly demanding conditions. The loads applied to the engine, and the harshness of the surrounding environment, place a great amount of stress on an engine. Therefore, consistent monitoring of the condition of the oil is increasingly important.
Currently, the condition of engine oil, i.e., when the useful life of the oil has ended, is estimated by monitoring the length of time the oil is in use, and modifying the estimate by accounting for the conditions under which the engine operates. The estimate is used to determine the interval, in time or mileage, between oil changes. However, the condition of the oil at any given time cannot be determined by this method.
In addition, the estimate may not accurately determine the useful life of the oil. Therefore, the oil may be changed too frequently, which adds unnecessary maintenance costs, or not frequently enough, which causes undue wear on the engine.
During combustion of fuel in an engine, some by-products of the fuel are deposited during each combustion cycle on the walls of each cylinder in an engine. One of these by-products, sulfur, combines with water and oxygen to form sulfuric acid. The rings on the pistons then wipe this sulfuric acid and additional sulfur off the cylinder walls and deposits these products into the oil that lies in the crankcase of the engine. The sulfur and sulfuric acid products reduce the total base number of the oil (TBN).
The TBN of the oil is a direct indicator of oil condition. For example, new oil may have a desired TBN of 10. As sulfuric acid is added to the oil, the TBN will decrease toward zero (and even become a negative number if the oil be allowed to become acidic). The TBN depletion of engine oil enables the acids in the oil to attack the metal linings of the engine, thus causing corrosion. The ability to monitor the TBN of the oil can help determine when the oil is nearing the end of its useful life.
The present invention is directed to overcoming one or more of the problems as set forth above.